This invention relates to a camera system capable of performing a high speed synchronized photography.
When taking a photograph in a dark place, it has been a common practice to use the auxiliary light emitted from a flash device in combination with the ambient light. However, in the case where a flash photography is executed by a camera having a focal plane shutter, there has been the likelihood that an object is not sufficiently illuminated by the flash light while the gap defined by front and rear blinds of the focal plane shutter travels across a film plane at a shutter speed greater than a flash synchronized shutter speed. In this case, the film plane is exposed partially by the flash light regardless of at which moment the flash device is fired, with the result that a uniformly exposed picture cannot be obtained.
In order to overcome this problem, U.S. Pat. No. 4,422,743 discloses a camera system which causes a flash device to selectively emit a first type of light which flashes instantaneously and a second type of light which flatly flashes for a prolonged period of time. The instantaneous flash light is emitted when a control shutter speed is smaller than the flash synchronized shutter speed. The flat flash light is emitted when a control shutter speed is greater than the flash synchronized shutter speed. Also, the instantaneous and flat flash lights are selectively changed in accordance with the intensity of the ambient light. The intensity and time of the flat flash light are changed in accordance with the control shutter speed.
Japanese Unexamined Patent Publication No. 61-98334 discloses a flash device including a semiconductor switching device which is connected in series with a flash light discharge tube and which is turned on and off at intervals of a minute time to emit flat flash light. Japanese Unexamined Patent Publication No. 64-17033 discloses a flash device which uses IGBT (Insulated Gate Bipolar Transistor) to emit a flat flash light. Similarly to U.S. Pat. No. 4.422,743, these flash devices emit flat flash light when a control shutter speed is greater than the flash synchronized shutter speed.
Further, there have been proposed a camera system which emits flat flash light when an object is closer to the camera than a predetermined distance (U.S. Pat. No. 4,354,751); a camera system which cannot emit flat flash light but can determine an optimal flash light intensity based on the shake limiting shutter speed and the flash synchronized shutter speed (U.S. Pat. No. 5,051,769, U.S. Pat. No. 5,144,359): and a camera system which cannot emit flat flash light but executes a preliminary light emission to calculate an optimal flash light intensity (U.S. Pat. No. 5,268.730).
In the aforementioned conventional camera systems, the flash photography mode is changed between the flat flash photography and the instantaneous flash photography by a manual operation in accordance with the discrimination result of whether or not a control shutter speed is greater than the flash synchronized shutter speed, or in accordance with the discrimination result of whether the photography mode is a macro photography mode or a normal photography mode. In such conventional manners, it has been very difficult to carry out photography which is optimal to reflect an operator's intention and a state of an object.
Further, flash devices used in the conventional camera systems do not calculate an amount of flash light in accordance with an automatic exposure calculation result, a distance to an object and the like. Accordingly, the conventional camera systems have required a skill of a certain level to obtain a picture free from an exposure error. Thus, it has been difficult for a novice to properly use these flash devices.